The Christian Social Union in Bavaria is a Christian democratic and conservative political party in Germany. Having a regionalist identity, the CSU operates only in Bavaria while its larger counterpart, the Christian Democratic Union (CDU), operates in the other fifteen states of Germany. It differs from the CDU by being somewhat more conservative in social matters, following Catholic social teaching. The CSU is considered the de facto successor of the Weimar-era Catholic Bavarian People's Party.

Bavaria, officially the Free State of Bavaria, is a state in the southeast of Germany. With an area of 70,550.19 km2 (27,239.58 sq mi), it is the largest German state by land area, comprising roughly a fifth of the total land area of Germany. With over 13 million inhabitants, it is the second most populous German state behind North Rhine-Westphalia, but due to its large physical size its population density is below the German average. Major cities include Munich, Nuremberg, and Augsburg.